Table 1: Summary of clinical characteristics and EEG features at presentation in early and childhood onset epileptic encephalopathy.

Epilepsy syndromeClinical featuresEEG features at presentation
Age of seizure onsetSeizure typesUnderlying etiologyPrognosisBackgroundInterictalIctal

Early infantile epileptic encephalopathy (ohtahara syndrome)First 2 weeks of lifeTonic seizuresCerebral structural abnormality, genetic abnormalities (i.e., STXBP1)25% die by 2 years or evolves to West syndrome and profound disabilitySuppression burst pattern in awake and sleepHigh voltage (150–350 uV) paroxysmGeneralized paroxysms or focal discharges

Early myoclonic encephalopathyFirst weeks of lifeMyoclonic seizures (erratic/fragmentary/
generalized); focal seizures
Metabolic genetic etiologies (nonketotic hyperglycinemia, pyridoxine/pyridoxal-5-phosphate dependency, molybdenum cofactor deficiency, organic aciduria, amino-acidopathies)50% die within first year or profound disabilitySuppression burst pattern, enhanced by sleepHigh voltage (150–350 uV) paroxysmGeneralized paroxysms or focal discharges

Migrating focal seizures in infancy3 monthsFocal motor seizures with autonomic manifestationsUnknown;
SCN1A, PLCB1, KCNT1 mutations;
2q24, 16p11.2 copy number variants
High mortality before 1 year or profound disability (cortical visual impairment; acquired microcephaly) Hemispheric background slowing Multifocal discharges, maximal in temporal and rolandic regionsRhythmic, monomorphic alpha or theta discharges in noncontiguous brain regions

West syndrome3–8 monthsEpileptic spasmsHeterogenous (congenital cortical malformations, tuberous sclerosis, trisomy 21, trisomy 18, CDKL5, ARX, MECP2)Depends on etiology; other seizure types evolve by about 5 yearsPoorly organized, high amplitude (500–1000 mV), generalized slowingMultifocal epileptiform discharges with generalized electrodecrementGeneralized sharp wave followed by electrodecrement

Dravet syndrome6 monthsFebrile status epilepticus, alternating hemiconvulsions→ absence, and myoclonic seizures80% SCN1A mutationMortality in childhood 10%, intellectual disability, or crouched gait without spasticity in adultsNormal, generalized or focal slowingGeneralized, multifocal or focal discharges; photoparoxysmal responseGeneralized paroxysms or focal discharges

ESES-related syndromes5–8 yearsFocal seizuresCSWS structural;
LKS unknown
Relapsing-remitting course or age limiting by teenage yearsNormal or focal/diffuse slowingFocal/multifocal/generalized discharges; marked sleep activation with increased interictal spatial distribution or bilateral synchrony; sleep spike wave index >85%;
CSWS-frontal predominant
LKS-temporal predominant
Focal discharges

Lennox-Gastaut syndrome1–8 yearsMultiple (tonic, atonic, absences, myoclonic, or focal)HeterogenousIntellectual disabilityNormal or generalized slowingFrequent slow spike waves 1.5–2.5 Hz or multifocalAbsence-low spike and waves; tonic-generalized attenuation with recruiting rhythm;
atonic-generalized polyspike/spike waves, or attenuation;
myoclonic-generalized polyspike/spike waves

Myoclonic-atonic epilepsy7 months–6 yearsMultiple (atonic, myoclonic, absences, or rarely tonic)No consistent etiology50% normal cognition at last followupNormal or mild diffuse/focal slowingGeneralized polyspike-and-wave discharges; photoparoxysmal responseGeneralized spike or polyspike-and-wave

Progressive myoclonic epilepsiesVaries by etiologyProminent myoclonic seizuresInborn errors of metabolism and mitochondrial disorders
(Tay-Sachs, Alpers syndrome, Lafora disease, Unverricht-Lundborg disease, or neuronal ceroid lipofuscinosis)
Developmental regression/dementia; mortality depends on etiologyGeneralized slowingGeneralized/multifocal discharges; photoparoxysmal response in Unverricht-Lundborg and neuronal ceroid lipofuscinosis
Generalized discharges

ESES: electrical status epilepticus in slow wave sleep; CSWS: continuous spike wave in sleep; LKS: Landau-Kleffner syndrome.